U.S. patent application number 17/594637 was filed with the patent office on 2022-08-11 for sterilization test pack.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to G. Marco Bommarito, Joshua D. Erickson, Jonathan C. Fuller, Andrew K. Hartzell, Timothy J. Nies, Michael J. Woodson.
Application Number | 20220249725 17/594637 |
Document ID | / |
Family ID | 1000006256684 |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220249725 |
Kind Code |
A1 |
Bommarito; G. Marco ; et
al. |
August 11, 2022 |
Sterilization Test Pack
Abstract
A sterilization test pack may include a shell defining an
indicator compartment having a volume; a channel extending between
a compartment opening and an exterior opening, the channel being in
fluid communication with the indicator compartment through the
compartment opening and surrounding atmosphere being in fluid
communication with the channel through the exterior opening such
that the indicator compartment is in fluid communication with the
surrounding atmosphere through the channel, the channel having a
length measured between the compartment opening and the exterior
opening and a hydraulic radius along the length; and an indicator
disposed in the indicator compartment, where a ratio of the
compartment volume to the channel hydraulic radius may range from
1000 cm.sup.2 to 8000 cm.sup.2.
Inventors: |
Bommarito; G. Marco;
(Stillwater, MN) ; Nies; Timothy J.; (Stillwater,
MN) ; Woodson; Michael J.; (West St. Paul, MN)
; Hartzell; Andrew K.; (Hudson, WI) ; Erickson;
Joshua D.; (Blaine, MN) ; Fuller; Jonathan C.;
(Oakdale, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000006256684 |
Appl. No.: |
17/594637 |
Filed: |
April 10, 2020 |
PCT Filed: |
April 10, 2020 |
PCT NO: |
PCT/IB2020/053453 |
371 Date: |
October 25, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62842218 |
May 2, 2019 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 2/28 20130101; A61L
2/206 20130101; A61L 2202/122 20130101; A61L 2/07 20130101; A61L
2202/24 20130101; A61L 2/208 20130101 |
International
Class: |
A61L 2/28 20060101
A61L002/28; A61L 2/07 20060101 A61L002/07; A61L 2/20 20060101
A61L002/20 |
Claims
1. A sterilization test pack comprising: a shell defining an
indicator compartment having a volume; a channel extending between
a compartment opening and an exterior opening, the channel being in
fluid communication with the indicator compartment through the
compartment opening and surrounding atmosphere being in fluid
communication with the channel through the exterior opening such
that the indicator compartment is in fluid communication with the
surrounding atmosphere through the channel, the channel having a
length measured between the compartment opening and the exterior
opening and a hydraulic radius along the length; and an indicator
disposed in the indicator compartment, a ratio of the compartment
volume to the channel hydraulic radius ranging from 1000 cm.sup.2
to 8000 cm.sup.2.
2. (canceled)
3. The sterilization test pack of claim 1, wherein the shell
comprises a top portion and a bottom portion
4-8. (canceled)
9. The sterilization test pack of claim 1, wherein the top and
bottom portions comprise polymeric film forming a pouch.
10-13. (canceled)
14. The sterilization test pack of claim 1, wherein the shell
comprises a support element constructed to receive the indicator
and to immobilize the received indicator within the indicator
compartment.
15. (canceled)
16. The sterilization test pack of claim 1, wherein the
sterilization test pack comprises only a single indicator
compartment and a single channel.
17. The sterilization test pack of claim 1, wherein the
sterilization test pack comprises two or more channels, each
channel extending from an exterior opening to a compartment opening
and providing a fluid connection between the indicator compartment
and the surrounding atmosphere.
18. The sterilization test pack of claim 1, wherein the two or more
channels comprise a first channel providing a first diffusivity and
a second channel providing a second diffusivity different from the
first diffusivity, and a closure configured to selectively close or
open at least one of the first and second channels.
19. A sterilization test pack comprising: a shell defining an
indicator compartment having a volume; a channel extending between
a compartment opening and an exterior opening, the channel being in
fluid communication with the indicator compartment through the
compartment opening and surrounding atmosphere being in fluid
communication with the channel through the exterior opening such
that the indicator compartment is in fluid communication with the
surrounding atmosphere through the channel, the channel having a
length measured between the compartment opening and the exterior
opening and a hydraulic radius along the length; and an indicator
disposed in the indicator compartment, the sterilization test pack
exhibiting a diffusivity (L.sub.D) of 0.02 cm to 50 cm.
20. (canceled)
21. The sterilization test pack of claim 19, wherein the length of
the channel is 30 mm or greater.
22-26. (canceled)
27. The sterilization test pack of any claim 19, wherein a ratio of
the compartment volume to the channel hydraulic radius is 1000
cm.sup.2 or greater.
28-35. (canceled)
36. The sterilization test pack of claim 19, wherein the shell
comprises a top portion and a bottom portion and wherein the top
and bottom portions comprise polymeric film forming a pouch.
37-40. (canceled)
41. The sterilization test pack of claim 19, wherein the shell
comprises a support element constructed to receive the indicator
and to immobilize the received indicator within the indicator
compartment.
42. (canceled)
43. The sterilization test pack of wherein the sterilization test
pack comprises only a single indicator compartment and a single
channel.
44. The sterilization test pack of claim 19, wherein the
sterilization test pack comprises two or more channels, each
channel extending from an exterior opening to a compartment opening
and providing a fluid connection between the indicator compartment
and the surrounding atmosphere.
45. The sterilization test pack of claim 44, wherein the two or
more channels comprise a first channel providing a first
diffusivity and a second channel providing a second diffusivity
different from the first diffusivity, and a closure constructed to
selectively close and open the first and second channels.
46. A sterilization test pack comprising: a shell defining an
indicator compartment having a volume of 15 cm.sup.3 to 300
cm.sup.3; a channel extending between a compartment opening and an
exterior opening, the channel being in fluid communication with the
indicator compartment through the compartment opening and
surrounding atmosphere being in fluid communication with the
channel through the exterior opening such that the indicator
compartment is in fluid communication with the surrounding
atmosphere through the channel, the channel having a length of 30
mm to 1000 mm measured between the compartment opening and the
exterior opening and a maximum hydraulic radius of 1.0 mm or less
at any selected location along the length; and an indicator
disposed in the indicator compartment.
47. The sterilization test pack of claim 46, wherein the
sterilization test pack exhibits a diffusivity (L.sub.D) of 0.02 cm
to 50 cm.
48-62. (canceled)
63. The sterilization test pack of claim 46, wherein the shell
comprises a support element constructed to receive the indicator
and to immobilize the received indicator within the indicator
compartment.
64-65. (canceled)
66. The sterilization test pack of claim 46, wherein the
sterilization test pack comprises two or more channels, each
channel extending from an exterior opening to a compartment opening
and providing a fluid connection between the indicator compartment
and the surrounding atmosphere.
67. The sterilization test pack of claim 66, wherein the two or
more channels comprise a first channel providing a first
diffusivity and a second channel providing a second diffusivity
different from the first diffusivity, and a closure constructed to
selectively close and open the first and second channels.
Description
FIELD
[0001] The present disclosure relates to test packs that can be
used to monitor and test the effectiveness of sterilization. In
particular, the present disclosure relates to test packs that can
be used to monitor and test the effectiveness of steam
sterilization.
BACKGROUND
[0002] In sterilization processes, sterilant gases like steam,
hydrogen peroxide, or ethylene oxide, may be used to sterilize a
load. The load may include items such as garments, tools, and
instruments. Monitoring sterilization processes generally involves
running chemical and/or biological indicators alongside each load
being sterilized. The indicators can either be placed with
instruments within each wrapped tray, or they can be processed in a
separate process challenge device.
[0003] Process challenge devices are designed to simulate the
resistance to sterilant penetration that is presented by the load
or an item within the load, which is dependent on the load item's
geometry and material, as well as the sterile packaging. When the
sterilant adequately penetrates the process challenge device and
sufficiently exposes the included biological and/or chemical
indicators, it provides assurance of sterility for the other load
items in the sterilizer chamber.
[0004] Biological indicators are used to gauge the effectiveness of
the sterilization procedure by monitoring the survival of a test
microorganism contained in the biological indicator. The test
microorganism is selected such that it is many times more resistant
to the sterilization process than most organisms. In order to test
the effectiveness of the sterilization cycle, the biological
indicator is placed in the sterilizer for the duration of the
cycle. After the sterilization cycle, the biological indicator is
removed and incubated under conditions that will promote the growth
of any surviving test microorganisms. If the sterilization cycle
failed, surviving microorganisms in the biological indicator
generate a detectable signal indicating that the sterilization
cycle was not effective.
[0005] Chemical indicators include one or more chemical components
that react to a particular condition, such as the presence of a
particular chemical or a temperature for a certain period of time.
Chemical indicators can be read immediately at the end of the
sterilization process. The results indicate only whether the
condition was present during the sterilization process.
[0006] One process control device commonly used in hospitals today
is the ATTEST.TM. Rapid 5 Steam Plus Test Pack available from 3M
Company in Maplewood, Minn. The Rapid 5 pack includes a stack of
paper medical index cards and an indicator embedded in a die-cut
cavity in the stack. The stacked cards are overwrapped with a
sterilization wrap and secured with an adhesive label. The Rapid 5
process control device is constructed to match the performance of
the AAMI (Association for the Advancement of Medical
Instrumentation) 16-towel pack, an industry standard which is
primarily a porous and absorbent load type.
SUMMARY
[0007] The present disclosure relates to test packs that can be
used to monitor and test the effectiveness of sterilization. In
particular, the present disclosure relates to test packs that can
be used to monitor and test the effectiveness of steam
sterilization.
[0008] According to one embodiment, the sterilization test pack may
include a shell defining an indicator compartment having a volume;
a channel extending between a compartment opening and an exterior
opening, the channel being in fluid communication with the
indicator compartment through the compartment opening and
surrounding atmosphere being in fluid communication with the
channel through the exterior opening such that the indicator
compartment is in fluid communication with the surrounding
atmosphere through the channel, the channel having a length
measured between the compartment opening and the exterior opening
and a hydraulic radius along the length; and an indicator disposed
in the indicator compartment, where a ratio of the compartment
volume to the channel hydraulic radius is from 1000 cm.sup.2 to
8000 cm.sup.2.
[0009] According to one embodiment, the sterilization test pack may
include a shell defining an indicator compartment having a volume;
a channel extending between a compartment opening and an exterior
opening, the channel being in fluid communication with the
indicator compartment through the compartment opening and
surrounding atmosphere being in fluid communication with the
channel through the exterior opening such that the indicator
compartment is in fluid communication with the surrounding
atmosphere through the channel, the channel having a length
measured between the compartment opening and the exterior opening
and a hydraulic radius along the length; and an indicator disposed
in the indicator compartment, where the sterilization test pack
exhibits a diffusivity (L.sub.D) of 0.02 cm to 60 cm or less.
[0010] According to one embodiment, the sterilization test pack may
include a shell defining an indicator compartment having a volume
of 15 cm.sup.3 to 300 cm.sup.3; a channel extending between a
compartment opening and an exterior opening, the channel being in
fluid communication with the indicator compartment through the
compartment opening and surrounding atmosphere being in fluid
communication with the channel through the exterior opening such
that the indicator compartment is in fluid communication with the
surrounding atmosphere through the channel, the channel having a
length of 30 mm to 1000 mm measured between the compartment opening
and the exterior opening, and a maximum hydraulic radius of 1.0 mm
at any selected location along the length; and an indicator
disposed in the indicator compartment.
[0011] The term "sterilant" is used in this disclosure to describe
a substance used during a sterilization process to kill
microorganisms. The substance is typically gaseous under the
sterilizing conditions. Examples of sterilants include steam,
hydrogen peroxide, and ethylene oxide.
[0012] The term "flexural modulus" is used in this disclosure to
refer to the tendency of a material to resist bending. Flexural
modulus can be measured using ASTM D790.
[0013] The term "heat deflection temperature" is used in this
disclosure to refer to the temperature at which a polymer or
plastic deforms under a specified load of 66 psi. Heat deflection
temperature can be measured using ASTM D648.
[0014] The term "hydraulic radius" is defined as the
cross-sectional area of flow in the channel divided by the wetted
perimeter of the channel Calculation of the hydraulic radius of the
channel (at a selected location) can be represented by the
following equation: hydraulic radius=(2.times.area of
channel)/(perimeter of channel).
[0015] The terms "integral" and "integrally formed" are used in
this disclosure to describe elements that are formed in one piece
(a single, unitary piece) and cannot be separably removed from each
other without causing permanent structural damage to the piece.
[0016] The term "transparent" is used in this disclosure to
describe a material that can be seen through with a naked eye. A
transparent material transmits at least 90% of electromagnetic
radiation having wavelengths in the visible spectrum (e.g., from
about 380 nm to about 740 nm). A transparent material may be
colorless or colored.
[0017] The term "opaque" is used in this disclosure to describe
materials that do not allow visible light to pass through. An
opaque material transmits less than 10% of electromagnetic
radiation having wavelengths in the visible spectrum (e.g., from
about 380 nm to about 740 nm). An opaque material may be colorless
or colored.
[0018] The term "semi-transparent" is used in this disclosure to
describe a material quality that is between opaque and transparent.
For example, it may be possible to see a liquid level through a
semi-transparent wall of a container.
[0019] The terms "plastic," "polymer" and "polymeric material"
refer to materials prepared from one monomer, such as a
homopolymer, and to materials prepared from two or more monomers,
such as a copolymer, terpolymer, or the like.
[0020] The term "pouch" refers to a pocket or bag shape that
deforms to accommodate objects placed therein.
[0021] The term "substantially" as used here has the same meaning
as "significantly," and can be understood to modify the term that
follows by at least about 75%, at least about 90%, at least about
95%, or at least about 98%. The term "not substantially" as used
here has the same meaning as "not significantly," and can be
understood to have the inverse meaning of "substantially," i.e.,
modifying the term that follows by not more than 25%, not more than
10%, not more than 5%, or not more than 2%.
[0022] The term "about" is used here in conjunction with numeric
values to include normal variations in measurements as expected by
persons skilled in the art and is understood have the same meaning
as "approximately" and to cover a typical margin of error, such as
.+-.5% of the stated value.
[0023] Terms such as "a," "an," and "the" are not intended to refer
to only a singular entity but include the general class of which a
specific example may be used for illustration.
[0024] The terms "a," "an," and "the" are used interchangeably with
the term "at least one." The phrases "at least one of" and
"comprises at least one of" followed by a list refers to any one of
the items in the list and any combination of two or more items in
the list.
[0025] As used here, the term "or" is generally employed in its
usual sense including "and/or" unless the content clearly dictates
otherwise. The term "and/or" means one or all of the listed
elements or a combination of any two or more of the listed
elements.
[0026] The recitations of numerical ranges by endpoints include all
numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5,
2, 2.75, 3, 3.80, 4, 5, etc. or 10 or less includes 10, 9.4, 7.6,
5, 4.3, 2.9, 1.62, 0.3, etc.). Where a range of values is "up to"
or "at least" a particular value, that value is included within the
range.
[0027] The words "preferred" and "preferably" refer to embodiments
that may afford certain benefits, under certain circumstances.
However, other embodiments may also be preferred, under the same or
other circumstances. Furthermore, the recitation of one or more
preferred embodiments does not imply that other embodiments are not
useful and is not intended to exclude other embodiments from the
scope of the disclosure, including the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1A is a perspective view of a sterilization test pack
according to an embodiment.
[0029] FIG. 1B is a perspective view of the bottom portion of the
sterilization pack of FIG. 1A.
[0030] FIG. 1C is a perspective view of the bottom portion of the
sterilization pack of FIG. 1A with indicators.
[0031] FIG. 2A is a top view of the bottom portion of the
sterilization pack of FIG. 1A.
[0032] FIG. 2B is a cross-sectional side view of the bottom portion
of the sterilization pack of FIG. 1A.
[0033] FIG. 3A is a perspective view of the bottom portion of a
sterilization test pack according to an embodiment.
[0034] FIG. 3B is a perspective view of the bottom portion of the
sterilization pack of FIG. 3A.
[0035] FIG. 4 is a top view of a sterilization test pack according
to an embodiment.
[0036] FIG. 5A is a perspective view of a layered structure of the
sterilization pack of FIG. 4.
[0037] FIG. 5B is a top view of a middle layer of the layered
structure of FIG. 5A.
[0038] FIG. 5C is a top view of a top layer the layered structure
of FIG. 5A.
[0039] FIG. 5D is a top view of a bottom layer of layered structure
pack of FIG. 5A.
[0040] FIG. 6 is a schematic view of a portion of a channel in a
sterilization test pack according to an embodiment.
[0041] FIG. 7 is a perspective view of a layered structure of a
sterilization test pack according to an embodiment.
[0042] FIG. 8 is a schematic depiction of a control test pack used
in the Examples.
DETAILED DESCRIPTION
[0043] The present disclosure relates to sterilization test packs
useful for testing the effectiveness of a sterilization procedure.
The sterilization test packs can be broadly categorized as
"lumen-challenge" test packs.
[0044] The performance of sterilization test packs may be compared
against a so-called towel test pack. The towel test pack includes a
stack of surgical towels and an indicator embedded in the stack.
While historically the AAMI 16-towel pack has proven to be one of
the most challenging items to sterilize, advancements in medical
instrumentation have created even more challenging items to be
sterilized.
[0045] It is common for medical instruments to include parts that
have a cavity or a lumen. Sterilizing such instruments is more
challenging than other instruments because the sterilant has to
reach through the entire cavity or lumen during the sterilization
process. Typical sterilization test packs of the AAMI 16-towel pack
are not able to adequately test or monitor sterilization of long
lumens. It would, therefore, be desirable to provide a
sterilization test pack that more accurately models sterilization
of instruments with a cavity or lumen.
[0046] A lumen-challenge test pack provides an increased resistance
against the sterilant to simulate a situation where an item with a
lumen (e.g., a medical instrument) is placed in the sterilizer and
the sterilization cycle is used to kill microorganisms inside the
lumen. The test pack generally includes a shell defining an
indicator compartment for holding a sterilization indicator, a
sterilization indicator, and a lid. During a sterilization
procedure, sterilant may enter the test pack through the lumen path
and contact the sterilization indicator. The challenge to the
sterilant penetration is provided by the lumen channel and an
indicator cavity volume.
[0047] FIG. 1A depicts one illustrative embodiment of a
sterilization test pack 1. The sterilization test pack 1 includes a
shell 10 formed by a bottom portion 200 and a top portion or cover
300. The shell 10 defines an indicator compartment 110 having a
volume V110 constructed or configured to house an indicator, such
as a biological indicator 401, a chemical indicator 402, or both.
The shell forms a channel 130 (e.g., lumen) that extends between a
compartment opening 132 and an exterior opening 131. The channel
130 is in fluid communication with the indicator compartment 110
through the compartment opening 132, and with the surrounding
atmosphere through the exterior opening 131, such that the channel
130 provides fluid communication between the indicator compartment
110 and the surrounding atmosphere (e.g., the sterilizer
chamber).
[0048] Generally, when the sterilization test pack 1 is in use, the
test pack is placed onto a sterilization tray along with the load
to be sterilized. The tray is then place in the sterilizer and a
sterilization cycle is initiated. During the sterilization cycle,
sterilant (for example, pressurized steam) enters the channel 130
(e.g., lumen) of the sterilization test pack 1 through the exterior
opening 131. The geometry of the channel 130 and the indicator
compartment 110 is designed such that it provides suitable
resistance to the sterilant and simulates the resistance to
sterilant penetration that is presented by the load. Examples of
parameters that influence sterilant resistance include the length,
hydraulic radius, and volume of the channel, and the volume of the
indicator compartment. Indicators included in the indicator
compartment indicate if the sterilization cycle was successful
(e.g., the sterilant successfully entered the indicator compartment
and sufficiently exposed the included biological and/or chemical
indicators to the sterilant).
[0049] The indicators may include a biological indicator 401 that
can be used to monitor the survival of a test microorganism
contained in the biological indicator. After the sterilization
cycle, the biological indicator is removed and incubated under
conditions that will promote the growth of any surviving test
microorganisms. If the sterilization cycle failed, surviving
microorganisms in the biological indicator generate a detectable
signal indicating that the sterilization cycle was not
effective.
[0050] The indicators may include a chemical indicator 402 that can
be used to monitor the presence of a particular condition, such as
the presence of a particular chemical or a temperature for a
certain period of time. Chemical indicators can be read immediately
at the end of the sterilization process to see whether the
condition was present during the sterilization process.
[0051] FIG. 1B is a perspective view of the bottom portion 200 of
the shell 10 without indicators. FIG. 1C is a perspective view of
the bottom portion 200 of the shell 10 with the indicators. FIGS.
2A and 2B show a top view and a cross-sectional view of the bottom
portion 200, respectively. According to one embodiment, the bottom
portion 200 forms a bottom wall 210 forming the indicator
compartment 110. For example, the bottom wall 210 may define a
self-supporting cup that forms the indicator compartment 110. The
indicator compartment 110 may be sized to accommodate one or more
indicators, such as a biological indicator 401, a chemical
indicator 402, or both. The indicator compartment 110 may further
be sized to provide a suitable back pressure to sterilant entering
the sterilization test pack 1 through the channel 130.
[0052] The indicator compartment 110 may have a volume V110 and a
depth D110. The volume V110 may be 15 cm.sup.3 (cubic centimeters,
also equal to milliliters, mL) or greater, 20 cm.sup.3 or greater,
30 cm.sup.3 or greater, 40 cm.sup.3 or greater, 50 cm.sup.3 or
greater, 60 cm.sup.3 or greater, 80 cm.sup.3 or greater, or 100
cm.sup.3 or greater. The volume V110 may be 300 cm.sup.3 or less,
250 cm.sup.3 or less, 200 cm.sup.3 or less, 150 cm.sup.3 or less,
130 cm.sup.3 or less, 120 cm.sup.3 or less, or 110 cm.sup.3 or
less. In some embodiments, the volume V110 ranges from 25 cm.sup.3
to 200 cm.sup.3, or from 40 cm.sup.3 to 125 cm.sup.3. The depth
D110 may be 15 mm or greater, 20 mm or greater, or 25 mm or
greater. The depth D110 may be 100 mm or less, 70 mm or less, 50 mm
or less, or 40 mm or less. In some embodiments, the depth D110
ranges from 15 mm to 70 mm, or from 20 mm to 50 mm.
[0053] The bottom wall 210 may include features that facilitate
placement or orientation of, and/or immobilize the indicators in
the indicator compartment 110. For example, the bottom wall 210 may
include one or more indicator support structures 212 constructed or
configured to receive one or more indicators. In FIGS. 1A-2C, the
indicator support structures 212 include protrusions that
facilitate placement or orientation of, and/or immobilize the
chemical indicator 402. In FIGS. 3A and 3B, the indicator support
structures 212 include a lip 2121 that facilitates placement or
orientation of, and/or immobilizes the chemical indicator 402, and
pockets 2122, 2123 that facilitate placement or orientation of,
and/or immobilize the biological indicator 401.
[0054] The bottom wall 210 may include features that provide
rigidity and/or stability to the sterilization test pack 1. For
example, the bottom wall 210 may include one or more reinforcing
structures (e.g., ribs) 214 (FIGS. 2A and 2B), 215 (FIG. 3B).
[0055] The bottom portion 200 may also include a flat portion 201
substantially surrounding the bottom wall 210. The flat portion 201
may be planar or substantially planar. The flat portion 201 may
facilitate attaching the top portion 300 to the bottom portion. For
example, the top portion 300 may be adhered to the flat portion
201. The top portion 300 and bottom portion 200 may be sealingly
coupled around the indicator compartment 110 outside of the channel
130. This may be achieved by adhering the top portion 300 to the
flat portion 201 only. When the test pack is assembled, the top
portion 300 may be flat or substantially flat.
[0056] In some embodiments, the top portion 300 is removable from
the bottom portion 200 without the use of tools. For example, the
top portion 300 may be peelable. The top portion 300 may include a
tab 310 or other feature to facilitate toolless removal.
[0057] The bottom portion 200 may also define the channel 130
extending across the flat portion 201 from the compartment opening
132 to the exterior opening 131. Alternatively, the channel 130 may
be formed by the top portion 300. The channel 130 has a length L130
and a hydraulic radius R130 measured anywhere along the length
L130.
[0058] An alternative embodiment of the sterilization test pack 1'
is shown in FIG. 4. The test pack 1 may have a bag or pouch-like
shape formed from polymeric sheets or films or other suitable
materials. The sterilization test pack 1' has a shell 10' formed by
a bottom portion 200' and a top portion or cover 300'. The interior
of the shell 10' defines the indicator compartment 110', which may
include one or more indicators, such as a biological indicator 401
and/or a chemical indicator 402. The indicator compartment 110' has
a volume V110'.
[0059] The sterilization test pack 1' includes laminated or layered
sheets shown in FIGS. 5A-5D. The sheets form at least a part of the
shell 10' of the test pack 1'. The sheets further form the channel
130' (e.g., lumen) that extends between a compartment opening 132'
and an exterior opening 131'.
[0060] The layered sheets include a three-layer laminate 303 shown
in FIG. 5A. The three-layer laminate 303 includes a lumen layer 330
sandwiched between a top layer 331 and a bottom layer 332. The
lumen layer 330 has an open lumen path 333 extending from a first
end 341 to a second end 342 (see FIG. 5B). When the lumen layer 330
is laminated between the top layer 331 and the bottom layer 332,
the open lumen path 333 forms the channel 130'. The channel 130'
has a length L130' and a hydraulic radius R130' along the length
L130'. The top layer 331 (see FIG. 5C) has an opening 131', which
aligns with the first end 341 of the lumen path 333 and forms the
exterior opening 131' of the channel 130'. The bottom layer 332
(see FIG. 5D) has an opening 132', which aligns with the second end
342 of the lumen path 333 and forms the compartment opening 132' of
the channel 130'.
[0061] The three-layer laminate 303 may form the top portion 300'
or part of the top portion 300' of the shell 10'. Alternatively,
the three-layer laminate 303 forms the bottom portion 200' or part
of the bottom portion 200' of the shell 10'. The opposite portion
(e.g., bottom portion 200' or top portion 300') may include a
single layer or another laminated sheet. The top and bottom
portions 300', 200' may be adhered or sealed together along their
edges. The three-layer laminate 303 may be adhered to the top
portion 300' or the bottom portion 200'. The shell 10' may include
a tab, notch, perforation, or other feature to facilitate opening
the shell 10' and removing the one or more indicators.
[0062] A similar laminated lumen construction (as the three-layer
laminate 303) may be used to apply a lumen to a shell with a bottom
portion that is a formed tray with a flat portion 302 surrounding
an indicator compartment 110.
[0063] The following features apply to each of the various
embodiments shown in the figures and discussed above unless
otherwise stated.
[0064] In some embodiments, the channel has the same or
substantially same cross section throughout its length. For
example, the channel hydraulic radius R130 may have a minimum value
and maximum value, where the maximum value is the same or up to 10%
greater, up to 25% greater, or up to 50% greater than the minimum
value. In such cases, the channel length L130 may be defined as the
entire length of the channel 130 between the compartment opening
132 and the exterior opening 131. The hydraulic radius R130 may be
determined anywhere along the channel length L130.
[0065] In an alternative embodiment, the hydraulic radius R130 of
the channel varies more significantly along the length of the
channel. For example, the hydraulic radius R130 may have a minimum
value defining a restricted portion 134, and a maximum value
defining an enlarged portion 136, where the maximum value is at
least 50% greater, at least 75% greater, or at least 100% greater
than the minimum value. See FIG. 6. In such cases, the restricted
portion 134 of the channel may be considered a lumen having a lumen
length L134, and the enlarged portion 136 may have an enlarged
channel length L136. For purposes of defining lumen challenge
(e.g., diffusivity) for sterilant penetration, the values of the
channel length 130 may be applied to the lumen length L134.
[0066] The dimensions of the test pack are selected to achieve
desired indicator performance in a sterilization cycle. For
example, the dimensions of the test pack are selected to achieve
desired indicator performance in gravity steam sterilization
cycles, dynamic-air-removal steam sterilization cycles, or both.
The dimensions may include one or more of channel length, channel
hydraulic radius, and indicator compartment volume. The dimensions
may be interrelated such that for a certain indicator compartment
volume, a suitable range of channel hydraulic radii may be
selected. Further, for a certain indicator compartment volume, a
suitable range of channel lengths may be selected.
[0067] The channel 130 may have a length L130 that is 30 mm or
greater, 50 mm or greater, 100 mm or greater, 150 mm or greater,
200 mm or greater, 300 mm or greater, 400 mm or greater, or 500 mm
or greater. The length L130 may be 1000 mm or less, 800 mm or less,
600 mm or less, 500 mm of less, 400 mm or less, or 300 mm or less.
In some embodiments, the length L130 ranges from 30 mm to 600 mm,
or from 50 mm to 400 mm.
[0068] The channel 130 may have a hydraulic radius R130 that is
0.10 mm or greater, 0.15 mm or greater, 0.17 mm or greater, 0.18 mm
or greater, 0.19 mm or greater, or 0.20 mm or greater. The
hydraulic radius R130 (e.g., the maximum hydraulic radius) may be
1.0 mm or less, 0.80 mm or less, 0.6 mm or less, 0.5 mm or less,
0.40 mm or less, or 0.35 mm or less. In some embodiments, the
hydraulic radius R130 ranges from 0.15 mm to 0.50 mm, or from 0.18
mm to 0.40 mm.
[0069] In some embodiments, the indicator compartment volume V110
and the channel hydraulic radius R130 have a ratio V110:R130 of 500
cm.sup.2 or greater, 800 cm.sup.2 or greater, 1000 cm.sup.2 or
greater, 1200 cm.sup.2 or greater, 1400 cm.sup.2 or greater, 1500
cm.sup.2 or greater, 1700 cm.sup.2 or greater, or 2000 cm.sup.2 or
greater. The ratio V110:R130 may be 8000 cm.sup.2 or less, 7000
cm.sup.2 or less, 6500 cm.sup.2 or less, 6000 cm.sup.2 or less, or
5000 cm.sup.2 or less. The ratio V110:R130 may range from 1000
cm.sup.2 to 7000 cm.sup.2 or from 1200 cm.sup.2 to 6000
cm.sup.2.
[0070] A channel cross sectional area A130 may also be calculated.
In some embodiments, the indicator compartment volume V110 and the
channel cross sectional area A130 have a ratio V110:A130 of 100 m
or greater, 110 m or greater, 125 m or greater, 150 m or greater,
200 m or greater, 300 m or greater, or 400 m or greater. The ratio
V110:A130 may be 1200 m or less, 1000 m or less, 800 m or less, or
600 m or less. The ratio V110:A130 may range from 100 cm to 1200 m
or from 110 m to 1000 m.
[0071] The relationship between the dimensions indicator
compartment volume V110, channel length L130, and channel hydraulic
radius R130 may also be expressed as a diffusivity (or scaled
diffusion length) L.sub.D. Diffusivity can be calculated as:
L D = { D + ( r h 3 8 .times. .mu. ) 2 .times. ( .DELTA. .times. P
L ) 2 .times. ( 1 48 .times. D ) } .times. t ; ##EQU00001##
where [0072] D is saturated steam (vapor) diffusion constant;
[0073] r.sub.h is hydraulic radius; [0074] .mu. is saturated steam
(vapor) viscosity; [0075] .DELTA.P is pressure difference across
the lumen; [0076] L is length of the effective lumen (represents
the length of the actual channel plus an additional length
proportional to a lumen volume equal to the volume of the chamber
and a hydraulic radius equivalent to that of the actual channel);
and [0077] t is time.
[0078] In some embodiments, the sterilization test pack has a
diffusivity L.sub.D of 0.02 cm or greater, 0.03 cm or greater, 0.05
cm or greater, 0.10 cm or greater, 0.20 cm or greater, 0.50 cm or
greater, 1.0 cm or greater, 1.5 cm or greater, 2.0 cm or greater,
2.5 cm or greater, 3.0 cm or greater, 4.0 cm or greater, 5.0 cm or
greater, 6.0 cm or greater, 8.0 cm or greater, 10 cm or greater, 12
cm or greater, 15 cm or greater, or 20 cm or greater. The
diffusivity L.sub.D may be 60 cm or less, 50 cm or less, 40 cm or
less, 35 cm or less, 30 cm or less, 25 cm or less, 20 cm or less,
or 15 cm or less. The diffusivity L.sub.D may range from 0.03 cm to
40 cm, or from 0.10 cm to 30 cm.
[0079] The shape of the indicator compartment 110 and the path of
the channel 130 are not particularly limited and may vary as shown,
for example, in FIGS. 1A, 3A, and 4. The indicator compartment 110
may have a more rectangular or elongated shape as shown in FIG. 1A,
or a more round or rounded square shape as shown in FIG. 3A. Other
shapes are, of course, also possible. In the alternative embodiment
shown in FIG. 4, the indicator compartment 110 assumes the shape of
the inside of the bag.
[0080] The channel 130 may follow any suitable path to accommodate
the length L130 of the channel 130. For example, the channel 130
may include straight sections, curved sections, or both, as shown
in the figures. In one embodiment shown in FIGS. 3A and 3B, the
channel 130 substantially surrounds the opening 111 of the
indicator compartment 110. The shape of the cross-section of the
channel 130 is not particularly limited and may be, for example,
polygonal (e.g., triangular or quadrilateral, such as square or
rectangular) or curved (e.g., arced, semicircular, or
semi-oval).
[0081] The shell 10 of the sterilization test pack 1 can be formed
by any suitable method. For example, the bottom portion 200 may be
formed by thermo forming, injection molding, blow molding,
machining, or a combination thereof. The bottom portion 200 may be
formed as a single integral piece. The top portion 300 may be
formed by extruding, laminating, or a combination thereof. The top
portion 300 may be adhered to the bottom portion 200 (e.g., the
flat portion 201) by an adhesive, heat bonding, or a combination
thereof.
[0082] According to some embodiments, the shell 10 or a portion of
the shell 10 is transparent or semi-transparent. For example, the
top portion 300 and/or the bottom portion 200 may be transparent or
semi-transparent or may include a transparent portion 302 or
semi-transparent portion. The entire shell may also be prepared
from a transparent or semi-transparent material such that the
contents of the indicator compartment are visible from multiple
angles. In some embodiments, the chemical indicator 402 is visible
through the shell. In some embodiments, both the chemical indicator
402 and the biological indicator 401 are visible through the
shell.
[0083] The bottom portion 200 and the top portion 300 may be
prepared from any suitable material and may be made from the same
or different materials. For example, in some embodiments the bottom
portion 200 may be prepared from a polymeric material, such as
polypropylene, polyethylene, polyethylene terephthalate (PET),
polycarbonate, polyolefin, polystyrene, polyacrylamide,
polymethacrylate, poly(methyl)methacrylate, polyimide, polyester,
polyethylene, terephthalate, polybutylene terephthalate,
polyvinylchloride, or a copolymer or a mixture thereof. In some
embodiments, the top portion 300 may be prepared from a polymeric
material, such as polypropylene, polyethylene, polyethylene
terephthalate (PET), mylar, metal foil, polyester, polyolefin,
polycarbonate, polyolefin, polystyrene, polyacrylamide,
polymethacrylate, poly(methyl)methacrylate, polyimide, polyester,
polyethylene terephthalate, polybutylene terephthalate,
polyvinylchloride, or a combination thereof. In some embodiments,
the bottom portion 200 and/or the top portion 300 may include
glass, ceramic, metal, or a combination thereof. For example, the
top portion 300 may be prepared from a polymeric material combined
with another material, such as a polymeric film co-extruded or
laminated onto a metallic film.
[0084] The sterilization test pack 1 may be constructed or
configured to have a desired level of rigidity to withstand
sterilization conditions. For example, the bottom portion 200 may
be prepared from a polymeric material having a suitable thickness
to provide a rigid or semi-rigid structure. The polymeric material
of the bottom portion may have a flexural modulus in the range of
500 MPa to 2500 MPa and a heat deflection temperature greater than
160.degree. F. The material and thickness may be selected so that a
suitable rigidity is achieved for the test pack as a whole. For
example, in some embodiments the bottom portion 200 is prepared
from polypropylene having a wall thickness of 0.50 mm or greater,
or 0.70 mm or greater, and 3.0 mm or less, 2.0 mm or less, or 1.0
mm or less.
[0085] In the bag-like embodiment shown in FIG. 4, the shell 10'
may be prepared from a suitable film and may include polymeric
materials and optionally metal (e.g., a metalized polymer film). In
some embodiments, the bottom portion 200', the top portion 300', or
both are prepared from polyethylene terephthalate (PET), mylar,
metal foil, polyester, polyolefin, polycarbonate, polyolefin,
polystyrene, polyacrylamide, polymethacrylate,
poly(methyl)methacrylate, polyimide, polyester, polyethylene
terephthalate, polybutylene terephthalate, polyvinylchloride, or a
combination thereof. In one embodiment, the three-layer laminate
303 is made from polyethylene terephthalate (PET). In one
embodiment, the bottom portion 200' and top portion 300' are made
from heat-sealable materials. The layers of the three-layer
laminate 303 may be adhered together using a suitable adhesive,
such as a pressure sensitive adhesive. Examples of suitable
pressure sensitive adhesives include silicone polyurea (SPU),
acrylics, silicones, and rubber-based adhesives. Alternatively, the
layers of the three-layer laminate 303 may be adhered together
using a suitable structural adhesive such as acrylic,
cyanoacrylate, epoxy, polyurethane, or a mixture thereof.
[0086] The films used to prepare the bottom portion 200' and top
portion 300' may independently have any suitable thickness, such as
0.5 mil or greater, 1 mil or greater, 2 mil or greater, 4 mil or
greater, or 6 mil or greater. The thickness of the films may be 100
mil or less, 50 mil or less, 40 mil or less, 25 mil or less, 10 mil
or less, or 5 mil or less. In some embodiments, the three-layer
laminate 303 is made from layers independently having a thickness
of 4 mil or greater, 6 mil or greater, 8 mil or greater, or 10 mil
or greater. The three-layer laminate 303 may be made from layers
independently having a thickness of 100 mil or less, 50 mil or
less, 40 mil or less, 25 mil or less, 10 mil or less, or 5 mil or
less. The layers of the three-layer laminate 303 may have the same
thickness or may have different thicknesses from one another. In
one embodiment, each of the layers of the three-layer laminate 303
independently have a thickness ranging from 2 mil to 50 mil, from 5
mil to 40 mil, or from 10 mil to 30 mil. Each of the layers (the
lumen layer 330, the top layer 331, and the bottom layer 332) may
further include sub-layers, where the layer itself is prepared from
multiple sub-layers.
[0087] The layers of the three-layer laminate 303 and the various
features in the layers may be prepared by any suitable method. For
example, the layers of the three-layer laminate 303 may be prepared
by punching, laser cutting, or etching the features onto the
respective layers before laminating the layers together. In one
embodiment, the lumen layer 330 is prepared by laser cutting,
punching, or etching the lumen path 333 onto a film, the top layer
331 is prepared by laser cutting, punching, or etching the opening
131' onto a second film, and the bottom layer 332 is prepared by
laser cutting, punching, or etching the opening 132' onto a third
film. The first, second, and third films may then be laminated or
bonded together (e.g., using an adhesive) such that the lumen layer
330 is sandwiched between the top layer 331 and the bottom layer
332, and the opening 131' aligns with the first end 341 of the
lumen path 333 and the opening 132' aligns with the second end 342
of the lumen path 333.
[0088] In the three-layer laminate 303, the channel hydraulic
radius R130 is determined by the thickness T330 of the lumen layer
330 and the width W333 of the lumen path 333. The thickness T330 of
the lumen layer 330 may be 4 mil or greater, 6 mil or greater, 8
mil or greater, or 10 mil or greater. The thickness T330 of the
lumen layer 330 may be 100 mil or less, 50 mil or less, 40 mil or
less, 25 mil or less, or 10 mil or less. The width W333 of the
lumen path 333 may be adjusted to arrive at a desired hydraulic
radius R130. The size (e.g., diameter or cross dimension) of the
openings 131', 132' may be selected to accommodate the size of the
lumen path 333. In some embodiments, the openings 131', 132' may
have a diameter or cross dimension of 1 mm or greater, 2 mm or
greater, or 3 mm or greater. The openings 131', 132' may have a
diameter or cross dimension of 10 mm or less, 7 mm or less, 5 mm or
less, or 4 mm or less.
[0089] According to some embodiments, the sterilization test pack 1
includes only a single indicator compartment 110. The single
indicator compartment 110 may house one or more indicators, such as
a biological indicator 401, a chemical indicator 402, or both.
[0090] According to some embodiments, the sterilization test pack 1
includes only a single channel 130 connecting the indicator
compartment to the exterior of the pack. In an alternative
embodiment, the sterilization test pack 1 includes two or more
channels 130. The two or more channels may be closed by a closure
(e.g., a seal, tab, or sticker), which may be selectively removed
or opened by a user. The channels 130 may be constructed or
configured to have different dimensions and thus different
diffusivity L.sub.D, allowing the user to select a level of
diffusivity most suited for the intended sterilization conditions.
An exemplary layered structure 1303 is shown in FIG. 7. For
example, the sterilization test pack 1 may include a first channel
1331 having a first level of diffusivity L.sub.D suitable for one
type of sterilization cycle (e.g., a gravity cycle), and a second
channel 1332 having a second level of diffusivity L.sub.D suitable
for another type of sterilization cycle (e.g., a pre-vacuum cycle).
The different levels of diffusivity L.sub.D may be achieved by
varying one or more of the parameters that affect diffusivity, such
as hydraulic radius or length. Prior to use, the exterior openings
of both channels may be closed by a closure. The user may prepare
the sterilization test pack by selectively opening one of the
channels by removing or opening the closure. The channels may be
independently formed, each having a separate exterior opening and
compartment opening, or may converge to share a common compartment
opening.
[0091] In one embodiment, the sterilization test pack 1 includes a
plurality of channels 130. The plurality of channels 130 may be
formed by using a micro-structured film. For example, the top
portion 300 may include a micro-structured film with a plurality of
channels formed between a micro-structured side of the film and the
flat portion 201 of the bottom portion 200. Suitable
micro-structured films are known from, for example, U.S. patent
numbers U.S. Pat. Nos. 5,728,446 and 5,514,120. In use, the
shortest path length formed from the edge of the micro-structured
film to the indicator compartment 110 would likely provide the path
of least resistance and thus act as the channel 130 for the
sterilant.
[0092] In the various embodiments of this disclosure, any suitable
indicators, including biological and/or chemical indicators, may be
used. For example, a biological indicator exhibiting a desired
resistance to the sterilant may be used. The resistance of the
biological indicator may contribute to the overall sterilization
test pack resistance. Thus, depending on the sterilization cycle
conditions used, a lower or higher resistance biological indicator
may be selected. Similarly, a chemical indicator that indicates
reaching of a desired sterilization condition (e.g., a certain
sterilization temperature) may be selected.
[0093] Typical steam sterilization temperatures range from
121.degree. C. to 135.degree. C. Further, typical sterilization
cycles include gravity cycles and pre-vacuum steam cycles. Due to
the differences between these two types of cycles, namely gravity
and pre-vacuum, different indicators and materials may be selected
to make the sterilization test pack for the respective cycle
type.
EXAMPLES
[0094] These examples are merely for illustrative purposes only and
are not meant to be limiting on the scope of the appended claims.
All parts, percentages, ratios, etc. in the examples and the rest
of the specification are by weight, unless noted otherwise. The
following abbreviations are used here: m=meter; cm=centimeter;
mm=millimeter; cm.sup.2=square centimeter; cm.sup.3=cubic
centimeter.
[0095] The performance of various types of sterilization test packs
was tested and evaluated against a control. The test packs were
tested using a gravity cycle and a pre-vacuum cycle.
Preparatory Example, Test Pack Type A
[0096] Test Pack Type A was prepared using a 2-mil (0.002 inches)
thick heat-sealable PET film (PERFECSEAL.RTM. #35881-E available
from Bemis Company, Inc. in Neenah, Wis.) to create an enclosed
pouch for housing a biological and a chemical indicator, and a
film-based lumen channel.
[0097] The 2-mil PET film pouch was sealed peripherally using a
handheld direct heat sealer. The heat seal width was between
0.25-0.5 inches, which created an adequate seal that could
withstand the autoclave temperature, pressure, and vacuum
conditions. The rectangular PET film pouches were sealed on three
(3) sides. The fourth side of the PET film pouch necessarily
remained open to allow for the eventual placement of the internal
biological and chemical indicator. The volume of the otherwise flat
PET film pouch was determined by filling the pouch with water and
pouring its filled contents into a graduated cylinder. A handheld
cork-borer was used to create a 0.125 inch diameter hole in one of
the two PET film layers. This 0.125 inch diameter hole is where the
lumen path would make fluid communication with the enclosed volume
of the PET film pouch.
[0098] The film-based lumen channel component of Test Pack Type A
was created by laminating multiple layers of SPU adhesive-coated
PET film. The SPU adhesive was 2-mils (0.002 inches) thick, and the
PET film was 10-mils (0.010 inches) thick. The top and bottom
layers of the lumen channel component were made up of a single
layer of PET film. The middle layer defining the lumen channel was
made by stacking one or more layers of the PET film to vary the
height. The adhesive-backed PET film was cut to shape using a laser
cutter. A 0.125-inch diameter hole was laser-cut into the top and
bottom layers of the lumen channel laminate, and these 0.125-inch
diameter holes functioned as the steam inlet into the lumen channel
and entrance into the enclosed PET film pouch. A lumen path was
laser cut into the middle layer, defining the length, width, and
height of the lumen channel. The number of stacked middle layers
determined the lumen channel height. The laser-cut tortuous path in
the middle layers defined the lumen length and lumen width. The
lumen channel width and height were used to calculate an effective
hydraulic radius of the lumen channel.
[0099] The bottom, middle, and top layers of the film-based lumen
channel were dry laminated together by hand, and then pressed in a
manual roller press to remove air bubbles in the adhesive bond line
and to increase adhesion of the press-sensitive adhesive. The
pressed film-based lumen laminate was then adhered to the PET film
pouch, aligning the 0.125-inch diameter holes of the pouch and the
bottom layer of the lumen channel component to fluidly connect the
PET pouch volume to the lumen channel. The entire construction was
then pressed using a manual roller to ensure adequate adhesion of
the lumen channel to the underlying PET film pouch. A biological
indicator and chemical indicator were inserted into the PET pouch
and the remaining open side of the PET film pouch was heat sealed.
The biological indicators were 3M.TM. ATTEST.TM. Biological
Indicators, and the chemical indicators 3M.TM. COMPLY.TM.
STERIGAGE.TM. Steam Chemical Integrators.
[0100] Test Pack Type A was similar to the test pack shown in FIG.
4. Samples 1-7 were of Type A, having dimensions shown in Table
1.
TABLE-US-00001 TABLE 1 Test Pack Type A. Test Pack PET Pouch
Channel Channel Channel Channel Type A Volume Height Width
Hydraulic Length Diffusivity Sample (cm.sup.3) (mm) (mm) Rad. (mm)
(cm) (cm) 1 115 0.25 0.76 0.19 15.2 0.03 2 82 0.25 0.76 0.19 15.2
0.06 3 115 0.25 0.76 0.19 5.1 0.27 4 82 0.25 0.76 0.19 5.1 0.53 5
115 0.51 0.76 0.30 15.2 4.92 6 82 0.51 0.76 0.30 15.2 6.47 7 115
0.51 0.76 0.30 5.1 29.70
Preparatory Example, Test Pack Type B
[0101] Test Pack Type B was prepared in a similar manner to Test
Pack Type A, except the indicator cavity volume was created using a
thermo-formed polypropylene tray with a heat-sealable aluminum foil
lidding material with a co-extruded polypropylene ("PP") sealant
layer. The thermo-formed tray was made from a 30-mil (0.030 inches)
thick PACUR.RTM. 7020 medical grade polypropylene film. The
heat-sealable aluminum foil lidding was Bemis L5103 material. A
handheld cork-borer was used to create a 0.125-inch diameter hole
in the aluminum foil lidding material to function as an inlet into
the indicator cavity.
[0102] The lumen channel of Test Pack Type B was created in the
same way as described for Test Pack Type A. The lumen channel
laminate was dry laminated and pressed to the sealant side of the
Bemis L5103 lidding material, being careful to align the 0.125-inch
diameter holes. A biological indicator and chemical indicator were
placed in the thermo-formed PP tray, and then a heated press was
used to bond the Bemis L5103 lidding with adhered lumen channel to
the underlying thermo-formed PP tray. The settings used to create
the heat seal were 100-PSI pressure, 365.degree. F. temperature,
for a dwell time of 2.5 seconds using a heated flat plate. The
biological indicators were 3M.TM. ATTEST.TM. Biological Indicators,
and the chemical indicators 3M.TM. COMPLY.TM. STERIGAGE.TM. Steam
Chemical Integrators.
[0103] Samples 8-10 were of Type B, having dimensions shown in
Table 2 below.
TABLE-US-00002 TABLE 2 Test Pack Type B. Test Pack PP Tray Channel
Channel Channel Channel Type B Volume Height Width Hydraulic Length
Diffusivity Sample (cm.sup.3) (mm) (mm) Rad. (mm) (cm) (cm) 8 49
0.51 0.76 0.30 35.6 3.30 9 49 0.76 0.66 0.35 35.6 14.60 10 49 0.76
0.76 0.38 35.6 30.70
Preparatory Example, Test Pack Type C
[0104] Test Pack Type C had a thermo-formed polypropylene tray
prepared in a similar manner to Test Pack Type B, except the lumen
channel was formed directly into the thermo-formed polypropylene
tray in the same thermo-forming operation step used to create the
indicator cavity volume. The thermo-formed tray was made from a
30-mil (0.030 inches) thick PACUR.RTM. 7020 medical grade
polypropylene film. The heat-sealable aluminum foil lidding was
Bemis L5103 material. The lumen channel cross-section was enclosed
by the thermo-formed polypropylene tray and the heat-sealable
aluminum foil lidding. The thermo-formed lumen path had an exterior
opening at the periphery of the tray and the lid, which functioned
as the steam entrance and exit point of the test pack.
[0105] Test pack type C was similar to the test pack shown in FIG.
1A. Sample 11 was of Type C, having dimensions shown in Table
3.
TABLE-US-00003 TABLE 3 Test Pack Type C. Test Pack PP Tray Channel
Channel Channel Channel Type C Volume Height Width Hydraulic Length
Diffusivity Sample (cm.sup.3) (mm) (mm) Rad. (mm) (cm) (cm) 11 49
0.51 0.76 0.30 15.2 18.00
Preparatory Example, Test Pack Control
[0106] The test pack control was prepared in accordance with
ANSI/AAMI ST79, using 16 clean, reusable, absorbent surgical
towels, each of which is approximately 16 inches.times.26 inches.
The towels were pre-conditioned at room temperature (65.degree. F.
to 75.degree. F., about 18.degree. C. to 24.degree. C.) with a
relative humidity at least 35% for a minimum of two (2) hours prior
to testing. Individual towels were first folded in thirds
lengthwise by folding one third over the middle third and the other
third under the middle third. Then, each towel was folded
width-wise in half, resulting in a folded towel of approximate
dimensions 9 by 9 inches. Sixteen (16) pre-folded towels were then
stacked to form a 16-towel pack of approximate dimensions 9 by 9 by
6 inches, with the towel folds alternating between layers. Four (4)
biological indicators and four (4) chemical indicators were placed
in the geometric center of the 16-towel pack, between the eighth
and ninth towel. The biological indicators were 3M.TM. ATTEST.TM.
Biological Indicators. The chemical indicators 3M.TM. COMPLY.TM.
STERIGAGE.TM. Steam Chemical Integrators. The 16-towel pack with
indicators was then secured using autoclave indicator tape.
[0107] The test pack control was similar to the test pack shown in
FIG. 8. Sample 12 was the Test Pack Control, having overall
dimensions of 9 by 9 by 6 inches and approximate dry weight of 3
pounds.
Test Methods
[0108] Method 1: Gravity Cycle
[0109] The evaluation of the lumen test packs (Types A, B, and C)
alongside the control AAMI 16-towel pack in gravity steam
sterilization cycles was performed in an AMSCO Eagle 3013C steam
sterilizer. The gravity cycle performance evaluation included two
main cycles, namely a 121.degree. C. and 132.degree. C. gravity
steam sterilization cycle. At each temperature, the performance of
the test packs was evaluated at two different exposure times,
including a fractional exposure and complete cycle (i.e., full
exposure). The gravity test cycle conditions are shown in Table 4
below.
TABLE-US-00004 TABLE 4 Sterilization Cycle Parameters. Gravity
Cycle 121.degree. C. 132.degree. C. Parameter Test Cycle Test Cycle
SKELETON GRAVITY GRAVITY STER TEMP 121.1 132.2 STER TIME
20:00-30:00 11:00-15:00 DRY TIME 5:00 5:00 DRY VAC 0.0 inHg 10.0
inHg PURGE 1:00 11p 0:51 6p FT 108 C. 108 C. FP 6 psig 6 psig STER
CTRL Drain Drain F0 SETPT 00 OFF 00 OFF OVERDRIVE 0.7 C. 0.7 C.
OVERTEMP 0.4 C. 0.4 C. UNDERTEMP 1.0 C. 1.0 C.
[0110] In each gravity test cycle, one (1) 16-towel pack (Control)
was run alongside three (3) or four (4) lumen test packs of Type A,
B, or C. All test packs were placed on the bottom level of the
sterilizer chamber and toward the front over the vessel drain.
[0111] Method 2: Pre-Vacuum Cycle
[0112] The evaluation of the lumen test packs (Types A, B, and C)
alongside the control AAMI 16-towel pack (Control) in dynamic-air
removal (i.e., pre-vacuum) steam sterilization cycles was performed
in two different steam sterilizers, namely an AMSCO Eagle 3013C and
Getinge 666-AC1 steam sterilizer. The 121.degree. C., 132.degree.
C., and 134.degree. C. pre-vacuum steam sterilization test cycles
were performed in the AMSCO 3013C autoclave, while the 135.degree.
C. pre-vacuum test cycles were performed in the Getinge 666-AC1
autoclave. The pre-vacuum test cycle conditions are shown in Table
5 and Table 6. The fractional cycles included the lower exposure
times and shorter pre-conditioning phases with fewer pulses.
TABLE-US-00005 TABLE 5 Sterilization Cycle Parameters. Pre-vacuum
121.degree. C. 132.degree. C. 134.degree. C. Cycle Parameter Test
Cycle Test Cycle Test Cycle SKELETON PREVAC PREVAC PREVAC STER TEMP
121.1 132.2 134.0 STER TIME 20:00-30:00 2:30-4:00 1:00-3:30 DRY
TIME 5:00 5:00 5:00 DRY VAC 0.0 inHg 0.0 inHg 0.0 inHg PULSES 2-4
2-4 2-4 P1 26.0 psig 26.0 psig 26.0 psig V1 10-24 inHg 10-24 inHg
10-24 inHg P1 HOLD 0:00 0:00 0:00 V1 HOLD 0:00 0:00 0:00 PURGE 1:00
6p 1:00 6p 1:00 6p FT 108 C. 108 C. 108 C. FP 6 psig 6 psig 6 psig
STER CTRL Drain Drain Drain F0 SETPT 00 OFF 00 OFF 00 OFF OVERDRIVE
0.7 C. 0.7 C. 0.7 C. OVERTEMP 0.4 C. 0.4 C. 0.4 C. UNDERTEMP 1.0 C.
1.0 C. 1.0 C.
TABLE-US-00006 TABLE 6 Sterilization Cycle Parameters. Pre-vacuum
135.degree. C. Cycle Parameter Test Cycle PULS 1 + LVL 2.068 BAR
PULS 2 + LVL 2.068 BAR PULS 3 + LVL 2.068 BAR PULS 1 - LVL 0.672
BAR PULS 2 - LVL 0.328 BAR PULS 3 - LVL 0.328 BAR PREVAC PULSES 3
PRE PLS RAMP NEG 4.751/M PRE PLS RAMP POS 0.600/M STER TRNSTN PNT
2.5 C. HEATUP PRESS RMP 4.751/M STER TEMP RAMP 150.0/M STERILIZE
TEMP 135.0 C. STERILIZE TIME 1:00-3:00 RAMP DRYING 4.751/M DRY VAC
DEPTH 0.328 BAR DRY TIME 5:00 POST PULSES 0
[0113] In each pre-vacuum test cycle, one (1) 16-towel pack
(Control) was run alongside three (3) or four (4) lumen test packs
of Type A, B, or C. All test packs were placed on the bottom level
of the sterilizer chamber and toward the front over the vessel
drain.
[0114] Method 3: Evaluation of Test Pack Performance
[0115] Upon completion of each gravity and pre-vacuum test cycle,
the biological indicators and chemical indicators were removed from
the lumen test packs and 16-towel pack (Control). The biological
indicators were incubated at 60.degree. C. for 7-days to test for
growth, and the run lengths of the STERIGAGE chemical indicators
were measured and recorded. For each test cycle condition, the
performance of the biological and chemical indicators in the
16-towel pack (Control) was compared to that of the lumen test
packs of Type A, B, and C. In the fractional exposure cycle, the
test pack Type A, B and C needed to show comparable performance to
that of the 16-towel pack (Control). This means an equal to or
greater number of surviving biological indicators and/or comparable
run length on the SteriGage moving front chemical integrators. In
the complete test cycles, where the cycles run to completion, the
test pack Type A, B, and C needed to show adequate kill of the
biological indicators and "Accept" results for the chemical
indicators. The comparison between the test pack Type A, B, and C
performance to that of the 16-towel pack (Control) are shown in
Table 7.
[0116] Results
[0117] Table 7 shows the performance of the test pack samples in
gravity and pre-vacuum steam sterilization cycles compared to the
performance of the same biological indicators and chemical
indicators in a 16-towel pack (Control).
TABLE-US-00007 TABLE 7 Test Pack Performance. Sample ID Diffusivity
Gravity Prevac Gravity Prevac Prevac Prevac (Type) (cm) 121.degree.
C. 121.degree. C. 132.degree. C. 132.degree. C. 134.degree. C.
135.degree. C. Sample 1 (A) 0.03 Hot Hot Hot ADQ ADQ ADQ Sample 2
(A) 0.06 Hot Hot Hot ADQ ADQ ADQ Sample 3 (A) 0.27 Hot Hot Hot ADQ
ADQ ADQ Sample 4 (A) 0.53 Hot Hot Hot ADQ -- -- Sample 8 (B) 3.30
Hot -- -- -- -- ADQ Sample 5 (A) 4.92 ADQ ADQ -- -- -- -- Sample 6
(A) 6.47 ADQ ADQ Cold Cold Cold Cold Sample 9 (B) 14.60 ADQ ADQ --
-- -- Cold Sample 11 (C) 18.00 ADQ ADQ ADQ Cold Cold Cold Sample 7
(A) 29.70 ADQ ADQ -- ADQ -- Cold Sample 10 (B) 30.70 ADQ ADQ -- --
-- Cold Sample 12 n/a ADQ ADQ ADQ ADQ ADQ ADQ (Control) Table 7
Legend: Cold = Indicates insufficient resistance to meet 16-towel
pack (Type C) equivalence ADQ = Indicates adequate 16-towel pack
(Type C) equivalence and adequate kill in complete cycle Hot =
Indicates resistance is too high, and adequate kill is not achieved
in complete cycle.
[0118] It was observed that creating a lumen-based test pack to
match the performance of the 16-towel pack (Control) across the
entire temperature range of 121.degree. C. to 135.degree. C. in
gravity and dynamic-air removal (i.e., pre-vacuum) steam
sterilization cycles is non-trivial. In general, higher resistance
to steam penetration in the high temperature pre-vacuum steam
sterilization cycles is helpful to match the 16-towel pack
performance. Conversely, less resistance is helpful to match the
16-towel pack performance in the low-temperature gravity steam
cycles.
[0119] It was observed that the test pack indicator cavity volume,
lumen channel length, and lumen channel radius play a significant
role in providing resistance to steam penetration. Additionally,
the extent to which these variables affect the test pack resistance
to steam penetration varies with the steam cycle type, namely
gravity or dynamic-air removal (i.e., pre-vacuum). In general, it
was observed that test pack resistance to steam penetration
increases as lumen length increases, lumen channel cross-section
decreases, and indicator cavity volume increases.
[0120] While performance in a certain type of sterilization cycle
is not limited to a test pack type, some of the aspects of the test
packs were found suitable for a given cycle type. Sample 11 is an
example of a lumen test pack construction particularly suitable for
gravity steam cycles. Samples 1, 2, 3, and 8 are examples of lumen
test pack constructions particularly suitable for dynamic-air
removal (i.e., pre-vacuum) steam cycles.
[0121] The resistance of the test pack to steam penetration may
also be influenced by the selection of the biological indicator.
However, if a biological indicator of inherently lower resistance
was used to repeat this evaluation, the comparative performance
between the test pack Type A, B, and C and the 16-towel pack
(Control) would not change. This is because the same indicators are
used in all the samples. However, the test packs that perform "hot"
in the lower-temperature gravity cycles, for example, would
potentially show adequate kill in complete cycles due to the lower
resistance of the biological indicator. Essentially, the inherent
resistance of the biological indicator shifts the resistance of the
entire test pack assembly up and down, in equal proportion, for
both the test pack types (lumen and 16-towel pack). The resistance
of the assembly can be analogized to an electrical circuit, where
the biological indicator and lumen test pack are essentially two
resistors in series, and increasing the resistance of the indicator
increases the resistance of the pack as a whole. This also holds
for the 16-towel pack, where the biological indicator and stack of
absorbent towels are two (2) resistors in series.
Test Pack Type B with Lower Resistance Indicator
[0122] To test the impact of a lower-resistance biological
indicator on the overall performance of the test pack, a series of
additional Type B test packs were assembled according to Sample 8
above, using 3M.TM. ATTEST.TM. Biological Indicators with lower
resistance.
[0123] Indicator resistance can be characterized using the D-value.
The term "D-value" or "decimal reduction value" refers to the time
required to achieve inactivation of 90% of a population of test
organisms (also known as a 1 log reduction). The D-value may be
expressed in minutes. The D-values of the biological indicators was
1.7 minutes at 121.degree. C. The lower Test D-value indicates
inherently lower resistance of the biological indicator.
[0124] The modified sample 8 with lower resistance biological
indicator was designated "Sample 8L." Table 8 shows the performance
of Sample 8L in a complete 121.degree. C./30-minute gravity cycle.
The performance of the Sample 8 test pack and 16-towel pack (type
C) are shown again for comparison.
TABLE-US-00008 TABLE 8 Test Pack Performance Sample ID Diffusivity
Gravity Prevac Gravity Prevac Prevac Prevac (Type) (cm) 121.degree.
C. 121.degree. C. 132.degree. C. 132.degree. C. 134.degree. C.
135.degree. C. Sample 8L 3.30 ADQ -- -- -- -- -- (B) Sample 8 3.30
Hot -- -- -- -- ADQ (B) Sample 12 n/a ADQ ADQ ADQ ADQ ADQ ADQ
(Control) Table 8 Legend: Cold = Indicates insufficient resistance
to meet 16-towel pack (Type C) equivalence ADQ = Indicates adequate
16-towel pack (Type C) equivalence and adequate kill in complete
cycle Hot = Indicates resistance is too high, and adequate kill is
not achieved in complete cycle.
[0125] Whereas Sample 8 exhibited resistance that was too high in
the 121.degree. C. gravity cycle (designated "Hot" in TABLE 8), it
was observed that Sample 8L with the lower-resistance biological
indicator showed adequate performance with 16-towel pack (Control)
equivalence and adequate kill in the complete cycle. While the
Sample 8L test packs with lower-resistance biological indicators
were not explicitly tested across the entire 121.degree.
C.-135.degree. C. steam sterilization cycle range, it can be
assumed that the relative resistance comparison between Sample 8L
test pack and the 16-towel pack (Control) with the same
lower-resistance biological indicators would not change. In this
way, one could deduce that Sample 8L could perform adequately
across the entire 121.degree. C.-135.degree. C. steam sterilization
cycle range.
[0126] All references and publications cited herein are expressly
incorporated herein by reference in their entirety into this
disclosure, except to the extent they may directly contradict this
disclosure. Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations can be substituted for the specific embodiments
shown and described without departing from the scope of the present
disclosure. It should be understood that this disclosure is not
intended to be unduly limited by the illustrative embodiments and
examples set forth herein and that such examples and embodiments
are presented by way of example only with the scope of the
disclosure intended to be limited only by the claims set forth
here.
* * * * *